New Clues for Cause of PMS Symptoms

Dec. 20, 2007 -- New research may help explain why some women experience
terrible symptoms with their monthly
periods while others do not.

Findings from a small, but intriguing, new study from Japan show significant
differences in heart rate variability among women, suggestive of a critical
role for the nervous system in premenstrual syndrome (PMS) and
its more severe form, premenstrual dysphoric disorder (PMDD).

The study focused on the part of the nervous system that controls
involuntary processes like heart beat, respiration, and digestion, known as the
autonomic nervous system (ANS).

The findings suggest that this area may be permanently depressed in women
with the most serious menstrual-cycle-related symptoms, researcher Tamaki
Matsumoto, PhD, tells WebMD.

"We have found that an imbalance in ANS may be a cause of PMS, but not
the only cause," she says. "However, the findings must be confirmed in
larger studies."

Causes of PMS

Most women who menstruate experience some degree of distress and discomfort
immediately before or during their monthly periods, and 3% to 8% have symptoms
severe enough to disrupt their lives and/or relationships, studies suggest.

There are many theories about the causes of PMS, but no definite
physiological trigger has been identified.

In the newly published study, Matsumoto and colleagues examined whether the
activity of the autonomic nervous system was altered during the menstrual
cycle.

Researchers measured heart rate and hormone level variability for the 62
women in their 20s to 40s with regular menstrual cycles. The women also filled
out questionnaires designed to evaluate physical, emotional, and behavioral
symptoms associated with menstrual cycles.

Heart rate variability throughout the month was measured as an indicator of
ANS activity.

The researchers found little differences in ANS activity during the month in
women with few or no symptoms of PMS, but significant decreased activity in
women with PMDD.

PMS and Heart Rate Variability

Women with PMS showed differences in heart rate variability around the start
of their monthly periods.

Women with PMDD also showed significantly decreased heart rate variability
throughout the month, suggesting that a permanently depressed nervous system is
linked to severe cycle-related symptoms.

"Does this imply that women with lower autonomic function regardless of
the menstrual cycle are vulnerable to more severe premenstrual disorders?"
Matsumoto and colleagues write. "Clinical research on the menstrual cycle
has been conducted from various perspectives. ... However, at the moment, the
underlying biomechanisms of PMS remain enigmatic."

If the findings are confirmed, heart rate analysis may prove to be of value
in the medical management of women with PMS and PMDD, Matsumoto says.

The study appears in the latest online version of the journal
BioPsychoSocial Medicine.